Gas-phase VUV photoionisation and photofragmentation of the silver deuteride nanocluster [Ag10D8L6]2+ (L = bis(diphenylphosphino)methane). A joint experimental and theoretical study

Steven Daly (1) , Marjan Krstić (2) , Alexandre Giuliani (3, 4) , Rodolphe Antoine (1) , Laurent Nahon (3) , Athanasios Zavras (5, 6) , George N. Khairallah (5, 6) , Vlasta Bonačić- Koutecký (2, 7) , Philippe Dugourd (1) , R a J O'Hair (5, 6)

1 ILM - Institut Lumière Matière [Villeurbanne]
2 Center of Excellence for Science and Technnology - Integration of mediterranean region (STIM)
3 SSOLEIL - Synchrotron SOLEIL
4 CEPIA - Département Caractérisation et Elaboration des Produits Issus de l'Agriculture
5 School of Chemistry - Bio21 Molecular Science & Biotechnology Institute [Melbourne]
6 ARC Centre of excellence for free radical chemistry
7 Institut für Chemie der Humboldt-Universität zu Berlin

The bis(diphenylphosphino)methane (L = Ph2PCH2PPh2) ligated silver deuteride nanocluster dication, [Ag10D8L6](2+), has been synthesised in the condensed phase via the reaction of bis(diphenylphosphino)methane, silver nitrate and sodium borodeuteride in the methanol : chloroform (1 : 1)mixed solvent system. The photoionisation and photofragmentation of this mass-selected cluster were studied using a linear ion trap coupled to the DESIRS VUV beamline of the SOLEIL Synchrotron. At 15.5 eV the main ionic products observed are [Ag10D8L5](2+), [Ag10D8L4](2+), [Ag10D8L6](3+center dot), [Ag9D8L4](2+center dot), and [AgL2](+). The later two products arise from fragmentation of [Ag10D8L6](3+center dot). An analysis of the yields of these product ions as a function of the photon energy reveals the onset for the formation of [AgL2](+) and [Ag9D8L4](2+center dot) is around 2 eV higher than that for ionisation to produce [Ag10D8L5](3+center dot). The onset of ionisation energy of [Ag10D8L6](2+) was determined to be 9.3 +/- 0.3 eV from a fit of the yield of the product ion, [Ag10D8L6](3+)center dot, as a function of the VUV photon energy. DFT calculations at the RI-PBE/RECP-def2-SVP level of theory were carried out to search for a possible structure of the cluster and to estimate its vertical and adiabatic ionisation energies. The calculated lowest energy structure of the [Ag10D8L6](2+) nanocluster contains a symmetrical bicapped square antiprism as a silver core in which hydrides are located as a mix of triangular faces and edges. Four of the bisphosphines bind to the edges of the cluster core as bidentate ligands, the remaining two bisphosphines bind via a single phosphorus donor atom to each of the apical silver atoms. The DFT calculated adiabatic ionisation energy for this structure is 8.54 eV, in satisfactory agreement with experiment.

Domaines: Chimie; Physique [physics]

Steven Daly, Marjan Krstić, Alexandre Giuliani, Rodolphe Antoine, Laurent Nahon, et al.. Gas-phase VUV photoionisation and photofragmentation of the silver deuteride nanocluster [Ag10D8L6]2+ (L = bis(diphenylphosphino)methane). A joint experimental and theoretical study. Physical Chemistry Chemical Physics, 2015, 17 (39), pp.25772 - 25777. ⟨10.1039/c5cp01160d⟩. ⟨hal-01344698⟩